The goal of this program is to evaluate compliance effects on the development of perianastomotic hyperplasia with small 4mm I.D. vascular grafts. Three types of composite grafts will be developed providing an identical blood contacting surface on different compliant elastomeric substrates. A composite impervious graft is composed of a textured and coated polyurethane covered with a biolized inner surface layer of protein. The unique feature of the biolized surface is that it is uniform, reproducible and applicable to different substrates. The addition of a smooth stable impervious 30 Mu layer of crosslinked gelatin (biolized surface) does not promote macroscopic deposition of either formed elements or blood proteins. This was demonstrated in many blood pump implant studies. The dimensions and mechanical properties of the substrate are independently controllable without affecting the blood compatibility of the gelaitn coating. Preliminary dog studies for up to 13 months demonstrate the need for the impervious biolized graft model. Using salt casting techniques, the finalized design for compliance testing includes three types of grafts: a) the non-compliant; b) the semi-compliant; and c) the compliance matched tubes. The elasticity of the graft to the natural vessel can be matched or varied with these three graft versions. After in-depth in vitro characterization of these grafts, a total of 60 six week implants will be performed in 30 dogs, and 30 six month implants in 15 dogs. Five cm tube grafts will be implanted alternating the three types of grafts in the right and left carotid replacement positions. Flow, pressure measurements and diameter changes at the anastomoses and at selected sites along the graft will be measured noninvasively immediately after implant and prior to autopsy. The proximal, distal and mid portions of the graft will be evaluated by routine histological methods as well as by SEM, SEM/EDX, and TEM. Statistical analysis will establish the relationship between the development of perianastomotic hyperplasia and the compliance nature of the vascular prosthesis. The success of this project will define if compliance matching is a necessary prerequisite for long term graft patency and function.